1. Field of the Invention
The invention is directed to an improved fuel injection system for an internal combustion engine and more particularly to such a system having a high pressure fuel pump and a fuel injection valve for each engine cylinder.
2. Description of the Prior Art
One fuel injection system known from German Patent Disclosure DE 198 35 494 A1 has one high-pressure fuel pump and one fuel injection valve communicating with it for each cylinder of the engine. The high-pressure fuel pump has a pump piston, driven in a reciprocating motion by the engine, that defines a pump work chamber which communicates with a pressure chamber of the fuel injection valve. The fuel injection valve has an injection valve member, by which at least one injection opening is controlled and which is movable, urged by the pressure prevailing in the pressure chamber, counter to a closing force in an opening direction to uncover the at least one injection opening. By means of a control valve actuated by a piezoelectric actuator, a connection of the pump work chamber with a relief chamber is controlled at least indirectly in order to control the fuel injection. When the pressure in the pump work chamber and thus in the pressure chamber of the fuel injection valve reaches the opening pressure, the injection valve member moves in the opening direction and uncovers the at least one injection opening. The injection cross section, which is controlled in the process by the injection valve member, is always the same size. This does not enable optimal fuel injection under all operating conditions of the engine.